Researchers at Australia’s University of Wollongong uncovered fossils that date as far back as 3.7 billion years in the rocks of the remote Isua Greenstone Belt in Greenland. If confirmed, these fossils will outdate what was once considered the earliest evidence of life on Earth by about 220 million years.

Some researchers believe microbes are the cause of formation for these structures, but there are critics who doubt this reasoning, including Riding.

“It is completely plausible that we could find stromatolites in rocks of Isua age, and perhaps even older, because available evidence suggests that the Earth’s surface at that time already had conditions suitable for microbial life,” said Riding in the interview with The Guardian. “We just need to find well-preserved sediments of that age to really be sure.”

The Isua Greenstone Belt is located near Nuuk, where travelers can enjoy everything from whale watching and skiing to viewing the Northern Lights.